1. Field of the Invention
This invention relates to optical transducers, and more particularly to optical transducers for determining position, orientation, direction, revolution, acceleration, fluid flow, torque, and the like.
2. Description of the Related Art
Prior art angular position transducers typically include a transparent encoder disk and a circumferential track imprinted thereon. A light source is positioned on one side of the disk in alignment with the track and a pair of spaced photodetectors are positioned opposite the light source on the other side of the disk. Typically, each track comprises a series of equally-spaced opaque bars separated by transparent sections. As the disk rotates, the bars and transparent sections cause the photodetectors to alternate between high and low states. A microprocessor typically receives the high and low states of each photodetector and determines the direction of disk rotation depending on which photodetector goes high or low first. The number of high or low states are then added or subtracted (depending on the direction of disk rotation) in order to determine the angular position of the encoder disk.
Although these types of transducers perform adequately for their intended purpose, they can be relatively difficult and costly to manufacture and their resolution is typically limited by the number of bars in the circumferential track, the spacing between bars, the relative size of the transducers, and other factors. The bars must be accurately positioned on the disk, and the light source and photodetectors must be positioned very accurately with respect to the bars so that direction of disk rotation can be ascertained.